KR20230056764A - Optical coherence tomography device and optical coherence tomography method - Google Patents

Abstract

Provided is an optical coherence tomography device that is unlikely to cause tomographic displacement even when it is portable and capable of taking tomography over a wide area at once, and an optical coherence tomography method using the same. An objective lens condensing light from a light source onto a sample is provided, and the sample is measured based on interference between sample light, which is reflected light from the sample, and reference light, which is reflected light from a reference surface provided between the objective lens and the sample. An optical coherence tomography apparatus that performs tomography, wherein both the sample light and the reference light pass through the objective lens, and the objective lens is an optical coherence tomography apparatus that is an Fθ lens.

Description

Optical coherence tomography device and optical coherence tomography method

The present disclosure relates to an optical coherence tomography apparatus and an optical coherence tomography method.

BACKGROUND OF THE INVENTION Optical Coherence Tomography (OCT) is mainly used for tomography of biological organs such as eyes in the medical field.

As an optical coherence tomography apparatus, light from a light source is divided by a beam splitter or the like, and reflected light is separately irradiated to a sample and a reference mirror to obtain reflected light, and tomography is performed using interference of these reflected light passing through separate optical paths. It is common (for example, refer to Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-104127

An object of the present disclosure is to provide an optical coherence tomography device capable of performing tomography of a wide area at once, and an optical coherence tomography method using the same, in which shifting of tomographic images is difficult to occur even when it is portable.

The present disclosure includes an objective lens for condensing light from a light source onto a sample,

An optical coherence tomography device that performs tomography of the sample based on interference between sample light, which is reflected light from the sample, and reference light, which is reflected light from a reference surface provided between the objective lens and the sample,

Both the sample light and the reference light pass through the objective lens,

The objective lens relates to an optical coherence tomography apparatus that is an Fθ lens.

It is preferable that the optical coherence tomography apparatus is configured to perform the tomography with the distance between the reference surface and the specimen being 0 to 3 cm.

The reference surface is preferably a plane of a reference member containing at least one selected from the group consisting of MgF ₂ , CaF ₂ , quartz, and sapphire.

It is preferable that both the sample light and the reference light are generated from light from the light source passing through the objective lens.

Preferably, the interference is created-type interference.

The optical coherence tomography apparatus further outputs the light from the light source to the side of the objective lens, and the sample light and reference light passing through the objective lens to the side of a detector that detects the sample light and reference light. It is preferable to provide a circulator outputting to .

The optical coherence tomography apparatus further includes a coupler that splits light from the light source into split light 1 used to generate the sample light and reference light, and split light 2 used to remove the DC component of the interference signal. And, it is preferable that the intensity ratio of split light 1 and split light 2 is 90:10 to 99:1.

It is preferable that the optical coherence tomography apparatus is configured so that a user can perform the tomography while carrying a part including the objective lens.

A part having the objective lens to be carried and a part not to be carried are connected via an optical fiber;

Preferably, the light from the light source and the sample light and reference light are transmitted through the optical fiber.

When the length of the optical fiber is 3 m or more, and the temperature difference between the atmosphere around the part equipped with the objective lens carried and the atmosphere around the part not carried is 1 ° C. or more, the deviation of the optical coherence tomography image obtained is It is preferable that it is 100 micrometers or less.

The present disclosure also relates to an optical coherence tomography method using any of the optical coherence tomography devices described above.

According to the present disclosure, it is possible to provide an optical coherence tomography device that is unlikely to cause misalignment of tomographic images even when it is portable and capable of taking tomography over a wide area at once, and an optical coherence tomography method using the same.

1 is a schematic diagram showing an example of a conventional optical coherence tomography (OCT) apparatus.
2 is a schematic diagram showing an example of the OCT device of the present disclosure.
3 is a schematic diagram showing another example of the OCT device of the present disclosure.
Fig. 4 is a diagram showing an OCT image obtained in Example 1;
Fig. 5 is a diagram showing an OCT image obtained in Comparative Example 1;
Fig. 6 is a diagram showing an OCT image obtained in Comparative Example 2;
Fig. 7 is a diagram showing an OCT image obtained in Reference Example 1;

In the medical field, an optical coherence tomography (OCT) apparatus using a Michelson interferometer as shown in FIG. 1 is generally used. In the OCT device 10 of FIG. 1, the light output from the light source 11 is divided by the coupler 12, and the reference light passing through the optical path including the circulator 13 and the reference mirror 14, Sample light passing through an optical path including the circulator 15 and the sample 16 is generated. The reference light and sample light are combined by a coupler 17, and an interference signal is detected by a photodetector 18.

In the medical field, usually, a probe having a sample optical path and an OCT device main body (housing) having a reference optical path are installed close to each other and used in the same room.

In contrast, in industrial fields and the like, there are cases where it is required to photograph an object in a place far away from the main body (housing) of the OCT device, such as outdoors, while carrying a probe. In this case, in the Michelson-type OCT device of FIG. 1 in which the sample light and the reference light pass through separate optical paths, a difference easily occurs in the environment (temperature, etc.) in which the sample optical path (probe) and the reference optical path (main body) are placed. , there is a problem that the shift (drift) of the obtained tomographic image increases due to the change in the optical path length.

In addition, OCT devices used in the medical field are focused on taking tomography of an extremely narrow range such as the eyeball with high precision, and there is also a problem that it is difficult to apply to fields requiring tomography of a wide area at once. .

As a result of intensive studies, the inventors of the present invention have found that the above problems can be solved by allowing both the sample light and the reference light to pass through the objective lens and employing an Fθ (F theta) lens as the objective lens. The OCT device of the disclosure was completed.

Hereinafter, the present disclosure will be described in detail.

The present disclosure is based on interference between sample light, which is reflected light from the sample, and reference light, which is reflected light from a reference surface provided between the objective lens and the sample, including an objective lens that condenses light from a light source onto a sample. An optical coherence tomography apparatus for performing tomography of the sample by performing tomography, wherein both the sample light and the reference light pass through the objective lens, and the objective lens is an Fθ lens.

In the OCT apparatus of the present disclosure, both sample light, which is reflected light from a sample to be imaged, and reference light, which is reflected light from a reference surface, pass through the objective lens. With this configuration, even when the part (for example, the probe) including the objective lens is made portable, no difference in the environment between the sample optical path and the reference optical path occurs, so that the obtained tomographic image has little deviation.

Further, the sample light and the reference light are incident from the sample side of the objective lens and are emitted toward the light source side.

The sample light and the reference light are generated from light from a light source. Light from the light source passes through an objective lens included in the OCT device of the present disclosure and is condensed on the sample. Reflected light from the sample becomes sample light. In addition, a part of the light from the light source is reflected on a reference surface provided between the objective lens and the sample, and becomes reference light.

Preferably, both the sample light and the reference light are generated from light from the light source passing through the objective lens. Compared to the case where the sample light and the reference light are separately generated from the divided light before passing through the objective lens, such as in the conventional Michelson type OCT device, the difference in the environment of the sample light path and the reference light path can be reduced, resulting in The shift of the tomographic image can be further reduced.

The objective lens included in the OCT device of the present disclosure is an Fθ lens. With this configuration, tomography can be performed over a wide area at once.

The Fθ lens is a lens that emits light incident at an angle θ with respect to the optical axis of the lens at a position of fθ from the optical axis of a surface perpendicular to the optical axis at the focal point, when the focal length of the lens is f.

The Fθ lens may be a telecentric Fθ lens or a non-telecentric Fθ lens.

The telecentric Fθ lens is an Fθ lens designed so that the chief ray is parallel to the optical axis of the lens, and is preferable in that a high-precision tomographic image can be obtained even if the distance between the lens and the sample fluctuates.

In the OCT device of the present disclosure, the light beam passing through the objective lens does not necessarily have to be telecentrically incident on the sample, but is incident in a state as close to telecentric as possible in terms of obtaining a higher-precision tomographic image. It is preferable to dispose the objective lens as much as possible.

The reference surface is preferably provided between the objective lens and the sample perpendicular to the optical axis of the objective lens.

The reference surface may be a surface that reflects at least a part of the light from the light source, but since it is easy to configure the sample light and the reference light to pass through a common optical path, a part of the light from the light source is transmitted and a part of the light is reflected. It is preferable that it is cotton. In this aspect, light transmitted through the reference surface is condensed on the sample to generate sample light, while light reflected by the reference surface becomes reference light.

The reference surface is preferably a plane of the reference member, and more preferably a surface of the reference member on the sample side.

It is preferable that the reference member transmits part of the light from the light source and reflects part of it.

Examples of the material constituting the reference member include crystalline materials, preferably crystals usable for optical windows, and specifically, MgF ₂ , quartz (SiO ₂ ), sapphire (Al ₂ O ₃ ), CaF ₂ , BaF ₂ , LiF, ZnSe, and the like. Especially, at least 1 sort(s) selected from the group which consists of _MgF2 , _CaF2 , quartz, and sapphire is preferable at the point which is excellent in chemical resistance.

One preferred embodiment is that the reference surface is a plane of a reference member containing at least one selected from the group consisting of MgF ₂ , CaF ₂ , quartz, and sapphire.

Preferably, the reference member is not subjected to a coating (for example, a coating for adjusting reflection).

The shape of the reference member may be a flat shape, and may be a plate shape, a cylinder shape, a prismatic shape, or the like, but a cylindrical shape is preferable. In the case of a cylinder shape, it does not necessarily have to be a garden pillar. In the case where the reference member further has a plane other than the reference plane, the reference plane and the other plane need not necessarily be parallel.

The thickness of the reference member (thickness in the optical axis direction) is, for example, preferably 1 to 50 mm, and more preferably 10 to 30 mm.

Further, when the thickness of the reference member is not constant, it is preferable that both the thickness of the thinnest part and the thickest part fall within the above range.

The reference member preferably satisfies the following relational expression (1).

nd≥Z _max (1)

(In the formula, nd represents the optical thickness of the reference member, and Z _max represents the measurable distance)

The optical thickness is the product of the refractive index of the reference member and the actual (geometric) thickness.

The measurable distance is expressed by the following relational expression (2).

Z _max =c/(4δf) (2)

(In the formula, c is the speed of light and δf is the frequency interval of OCT interference signal sampling)

If a reference member that satisfies relational expression (1) is used, a signal based on back reflection from the rear basal plane of the reference member (the surface on the opposite side of the reference plane) is within the tomographic image (a range corresponding to a depth greater than 0 and less than Z _max ). inside), a more highly accurate tomographic image can be obtained.

The reference member more preferably satisfies the following relational expression (3).

n×WD>nd>n×Z _max (3)

(In the formula, n represents the refractive index of the reference member. WD represents the working distance of the OCT device. nd and Z _max are as described above.)

The working distance is the distance from the foremost surface of the objective lens on the sample side to the sample when focused.

If a reference member that satisfies relational expression (3) is used, the intensity of the ghost image based on the back reflection from the rear basal plane (surface opposite to the reference plane) of the reference member can be reduced, resulting in a higher-precision tomographic image. You can get it.

In view of further reducing the strength of the ghost image based on the back reflection, the thickness of the reference member is preferably thicker within a range that satisfies the relational expression (3). It is also preferable to incline the rear base surface of the reference member with respect to the reference surface.

The effect described above becomes particularly remarkable when an anti-alias filter (low-pass filter) described later is provided.

It is particularly preferable that the reference member satisfies the following relational expression (4).

nd=m×Z _max (4)

(In the formula, nd and Z _max are as described above. m represents an integer greater than or equal to 1)

m is preferably an integer of 1 or more and 20 or less, and preferably an integer of 1 or more and 10 or less.

If a reference member that satisfies relational expression (4) is used, a signal based on back reflection from the rear basal plane of the reference member (the surface opposite to the reference plane) is transmitted to the end of the tomographic image (position corresponding to depth 0 or Z _max ). Since it overlaps with , the effect on the tomographic image is small, and a tomographic image with higher precision can be obtained.

The OCT device of the present disclosure may include the reference surface (reference member).

The OCT apparatus of the present disclosure is preferably configured to be capable of performing the tomography imaging while setting the distance between the reference surface and the sample to be 0 to 3 cm. When the reference plane and the sample can be brought closer in this way, the working distance is shortened, the noise is reduced, the resolution is increased, and the depth of the sample is in focus, which is preferable in that a tomographic image clear to the depth is obtained. Since the OCT device of the present disclosure uses an Fθ lens as an objective lens, it is possible to perform tomography with high accuracy even when the distance between the reference surface and the sample is short as described above.

Of course, it may also be possible to perform tomography with the distance between the reference surface and the sample larger than the above.

The light source may be a low-coherence light source, and is preferably a frequency scanning light source that scans while changing the frequency (wavelength) temporally.

As the frequency scanning light source, a wavelength sweeping laser using a wavelength sweeping filter (driving by a polygon mirror, driving by a galvano mirror, etc.), FDML laser, MEMS wavelength sweeping light source (MEMS VCSEL, external resonator type MEMS Fabry Pero laser, etc.) , SGDBR laser, etc. can be used.

Examples of the light beam output from the light source include visible light and infrared light, and near infrared light (NIR) is preferable. As the light ray, it is preferable to use a light ray having a wavelength of 800 to 2000 nm. Among them, light rays having a central wavelength of 940±50 nm, 1100±50 nm, 1310±50 nm, 1550±100 nm, or 1750±100 nm are more preferable from the viewpoint of the stability of the light source and the reliability of the sensor.

The OCT device of the present disclosure may include the light source.

The OCT apparatus of the present disclosure performs tomography imaging of the sample based on interference between the sample light and the reference light. In principle, the interference can be any one in which both the sample light and the reference light can pass through the objective lens, but it is preferably a fabrication-type interference or a Mirau-type interference, and more preferably a fabrication-type interference.

Types of OCT that can be employed in the OCT apparatus of the present disclosure include time domain OCT (TD-OCT), Fourier domain OCT (FD-OCT), and the like. As the FD-OCT, spectral domain OCT (Spectral Domain OCT: SD-OCT), frequency scanning OCT (Swept Source OCT: SS-OCT), and the like are exemplified. Among them, SS-OCT is preferred because of its high sensitivity and deep measurable depth.

The OCT device of the present disclosure preferably also includes a collimator that converts the light from the light source into collimated light. The collimator is preferably provided on an optical path between the light source and the objective lens.

The OCT device of the present disclosure preferably further includes a scanning mirror for scanning light from the light source focused on the sample. The scan mirror is preferably provided on an optical path between the light source and the objective lens, and more preferably provided on an optical path between the collimator and the objective lens.

As said scanning mirror, a galvano mirror, a polygon mirror, a MEMS mirror, etc. are mentioned. Especially, a galvano mirror is preferable, a 1-axis or 2-axis galvano mirror is more preferable, and a 2-axis galvano mirror is still more preferable.

It is preferable that the OCT device of the present disclosure further includes a driving device for driving the scanning mirror.

The OCT device of the present disclosure further outputs light from the light source to the side of the objective lens, and outputs the sample light and reference light passing through the objective lens to the side of a detector that detects the sample light and reference light. It is preferable to provide a circulator that outputs. In this aspect, the sample light and the reference light can be transmitted by one circulator. With this configuration, the device can be miniaturized and the cost can be reduced as compared with the case where the circulators through which the sample light and the reference light pass are separately provided as shown in FIG. 1 .

It is preferable that the said circulator has three or more ports, and it is more preferable to have three ports.

The circulator is preferably provided on an optical path between the light source and the objective lens, and more preferably provided on an optical path between the light source and the collimator.

In the case of a 3-port circulator, light from the light source is input from a first port on the side of the light source and output from a second port on the side of the objective lens. The sample light and reference light passing through the objective lens are input from a second port and output from a third port on the side of the detector.

The OCT device of the present disclosure preferably further includes a detector (also referred to as detector 1) that detects the sample light and the reference light. The detector 1 preferably detects an interference signal caused by the sample light and the reference light.

Detector 1 is preferably a differential photodetector. The detector 1 may have a function of amplifying a signal. Moreover, you may provide an amplifier separately.

In the OCT device of the present disclosure, a coupler (coupler ( Also referred to as 1)) is preferably provided. The coupler 1 is preferably provided on an optical path between the light source and the objective lens, and more preferably provided on an optical path between the light source and the circulator.

When the coupler 1 is provided, the intensity ratio of the divided light 1 and the divided light 2 is preferably 90:10 to 99:1, more preferably 92:8 to 98:2. By dividing by this intensity ratio, the DC component can be effectively removed from the interference signal.

It is preferable that the OCT device of the present disclosure further includes a detector (also referred to as detector 2) that detects split light 2. The detector 2 may be the same detector as the detector 1 described above, or may be a different detector.

It is preferable that the OCT device of the present disclosure further includes an attenuator for attenuating the divided light 2. As the attenuator, a variable optical attenuator (VOA) is preferable. The attenuator is preferably provided on an optical path between the coupler 1 and the detector 2 that detects the split light 2.

The OCT device of the present disclosure also preferably includes a data acquisition (DAQ) device that collects interference signals caused by the sample light and the reference light. The DAQ device preferably includes an A/D converter. Preferably, the DAQ device converts the collected interference signals into digital data.

The OCT device of the present disclosure preferably includes an anti-alias filter (also referred to as a low-pass filter) that attenuates unnecessary frequency components exceeding the measurable distance (Z _max ). The anti-alias filter is preferably provided on an optical path between the above-described detector 1 and the DAQ device.

It is preferable that the OCT device of the present disclosure further includes an arithmetic device for generating an optical coherence tomography image based on the interference signals of the sample light and the reference light. The arithmetic unit creates an optical coherence tomography image by imaging the interference signal according to characteristics such as intensity.

The OCT device of the present disclosure preferably further includes a display device for displaying the obtained optical coherence tomography image. The display device may be of a stationary type or a portable type, but a portable type is preferable because images can be confirmed at the shooting site. In addition, the connection with the said arithmetic device may be wired or wireless. The display device may be one or plural.

An example of the OCT device of the present disclosure is shown in FIG. 2 , but the OCT device of the present disclosure is not limited thereto.

In the OCT device 100 of FIG. 2 , the frequency scanning light source 101 outputs light used for OCT. The frequency scanning light source 101 outputs a trigger signal at each start of frequency scanning. In addition, light is detected by a Mach-Zehnder interferometer, and K clock signals for sampling at equal frequency intervals are output.

In the coupler 102, the light output from the frequency scanning light source 101 is split light 1 used to generate the sample light and reference light and split light 2 used to remove the DC component of the interference signal at a ratio of 95:5. is divided by the intensity ratio of Split light 1 is input to port 1 of circulator 103, output from port 2, and transmitted to probe 104 through an optical fiber with a length of several meters.

In the probe 104, the split light 1 is converted into parallel light by the collimator 105, reflected by the galvano mirror 106, and incident on the objective lens 107 as the Fθ lens. The galvano mirror 106 is driven by the galvano mirror driver 111 and scans the collimated light in the XY direction perpendicular to the optical axis. The parallel light incident on the objective lens 107 passes through the reference member 108, is condensed on the sample 110 to be photographed, is reflected on the sample surface, and enters the objective lens 107 as sample light. In addition, a part of the parallel light incident on the objective lens 107 is reflected in the reference plane 109 of the reference member 108 and enters the objective lens 107 as reference light.

The sample light and reference light incident on the objective lens 107 pass through the galvano mirror 106 and the collimator 105, are input to port 2 of the circulator 103 through an optical fiber, and are output from port 3. , which is then input to the differential photodetector amplifier 113. The differential photodetector amplifier 113 detects and amplifies an interference signal based on the interference of the sample light and the reference light.

The split light 2 split in the coupler 102 is attenuated by the variable optical attenuator 112 and then input to the differential photodetection amplifier 113 . The differential photodetector amplifier 113 uses the signal of split light 2 to remove the DC component included in the interference signal.

The DC component is removed by the differential photodetector amplifier 113, and the amplified interference signal is collected by a DAQ device (A/D converter) included in the PC 114 and converted into digital data. The collection of the interference signal is initiated by a trigger signal emitted by the frequency scanning light source 101 and is performed in synchronization with the K clock signal. In addition, an anti-alias filter (not shown) is provided between the differential photodetector amplifier 113 and the DAQ device to attenuate unnecessary frequency components exceeding the measurable distance (Z _max ).

An arithmetic unit included in the PC 114 generates an optical coherence tomography image of the sample 110 based on the interference signal converted by the DAQ device, and displays it on the mobile display 115 .

The OCT apparatus of the present disclosure is preferably configured such that the user can perform the tomography imaging while carrying the part including the objective lens. In the OCT device of the present disclosure, even when the portion including the objective lens is made portable in this way, there is no difference in the environment between the sample optical path and the reference optical path, so that the resulting tomographic image has a small discrepancy.

It is preferable that the portion including the objective lens further includes the reference surface (or reference member), the collimator, and the scanning mirror.

The portion including the objective lens is preferably a probe of an OCT device.

The OCT apparatus of the present disclosure is preferably configured so that the user can perform the tomography scan while holding the part including the objective lens in his hand, and the user holds the part including the objective lens in his hand and It is more preferable to be configured so that tomography can be performed.

The OCT device of the present disclosure may include a portion that can be carried by the user during tomography imaging, in addition to the portion including the objective lens. As the said part, the driving device for driving the said scanning mirror and the said display device are mentioned, for example.

In the OCT device of the present disclosure, a part having the objective lens to be carried and a part not to be carried are connected via an optical fiber, and the light from the light source and the sample light and reference light are transmitted through the optical fiber. desirable. In this aspect, even when the subject to be photographed is located at a place far away from the non-portable part, tomography can be performed by positioning the part including the objective lens near the subject by adjusting the length of the optical fiber. Since the light from the light source, the sample light, and the reference light are all transmitted through the optical fiber, even when the optical fiber is lengthened, there is no difference in environment between the sample optical path and the reference optical path, and the resulting tomographic image has a small discrepancy. In addition, because of the streamlined shape using the optical fiber, high-resolution OCT measurement can be performed even on a subject to be photographed at a location far away from the non-portable part.

The length of the optical fiber is not particularly limited and can be determined depending on the location of the subject to be photographed, but may be, for example, 1 m or longer, preferably 3 m or longer, more preferably 5 m or longer, and still more preferably 10 m or longer. Moreover, 100 m or less may be sufficient and 50 m or less may be sufficient.

It is preferable that the non-portable part includes, for example, the light source, the circulator, the detector, the DAQ device, and the arithmetic device.

It is preferable that the non-portable portion is the OCT device main body (housing).

When there is a portable part other than the part having the objective lens, the connection between the part and the part having the objective lens or the part not being carried is not necessarily limited to the connection by an optical fiber, and for example, a wire may be connected by

The OCT device of the present disclosure is obtained when the length of the optical fiber is 3 m or more, and the temperature difference between the atmosphere around the part having the objective lens carried and the atmosphere around the part not carried is 1 ° C. or more. It is preferable that the deviation of the optical coherence tomography image is 100 µm or less.

In the industrial field or the like, there are cases where an object to be photographed is in a place far away from the main body (housing) of the OCT device, outdoors, or in a high- or low-temperature facility. In this case, since a large difference occurs in the environment (temperature) of the probe and the body of the OCT device, in the OCT device where the sample light path is on the probe side and the reference light path is on the body side, this is due to the difference in the environment between the sample light path and the reference light path. A large discrepancy occurs in the resulting tomographic image. On the other hand, in the OCT device of the present disclosure, even in the above case, no difference in the environment between the sample optical path and the reference optical path occurs, so that the resulting tomographic image has a small discrepancy.

The length of the optical fiber in the above aspect is preferably 3 m or longer, more preferably 5 m or longer, and still more preferably 10 m or longer. Moreover, 100 m or less may be sufficient and 50 m or less may be sufficient.

The temperature difference between the atmospheres in the above aspect is preferably 1°C or higher, more preferably 5°C or higher, and still more preferably 10°C or higher. Moreover, it is preferable that the said temperature difference is 50 degrees C or less.

The shift of the optical interference tomography image is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less.

The misalignment (ΔZ) is expressed by the following formula (A):

ΔZ(㎛)=dn/dT(1/℃)×L(m)×10 ⁶ ×2×Δt(℃) (A)

(Wherein, dn/dT is the temperature coefficient of refractive index of the optical fiber material (1/°C), L is the length of the optical fiber (m), and Δt is the temperature difference (°C) between the sample optical path and the reference optical path)).

Said ΔZ is the shift|offset|difference of an optical distance.

When the material of the optical fiber is quartz glass, the wavelength of light is 1.3 μm, and the temperature is around room temperature, dn/dT is about 1.9×10 ^-5 (1/°C).

In an OCT device in which the sample optical path is on the probe side and the reference optical path is on the main body side, the temperature difference between the atmosphere around the part equipped with the objective lens to be carried and the atmosphere around the part not to be carried is almost the same as that of the optical path. Since it is reflected in the temperature difference Δt, the deviation ΔZ of the obtained tomographic image is large. On the other hand, in the OCT device of the present disclosure, even when the temperature difference between the atmosphere around the part having the objective lens carried and the atmosphere around the part not carried is large, the temperature difference Δt of the optical path is extremely small. ΔZ is also extremely small.

Another example of the OCT device of the present disclosure (an example in which the portion including the objective lens is a portable type) is shown in FIG. 3 , but the OCT device of the present disclosure is not limited thereto.

3, the user 201 carries the probe 202 of the OCT device in one hand and carries a galvano mirror driver 205 for driving a galvano mirror built in the probe 202 on the waist. there is. The probe 202 is connected to the housing 206 of the OCT device through an optical fiber 203. The galvano mirror driver 205 is connected to the probe 202 and the housing 206 via a wire 204.

In the housing 206, a light source, a detector, a DAQ device, an arithmetic device, and the like are stored.

The OCT device of the present disclosure is preferably configured so that the area in the plane direction capable of imaging with a resolution of 10 μm or more is in the range of 0.1 to 14 mm in length and 0.1 to 14 mm in width per one tomography scan using the light source described below. . Thereby, tomography can be performed with high precision over a wide area at once (even when different light sources are used).

(light source)

AXSUN high-speed wavelength sweep light source (center wavelength: 1310 nm, sweep width: 100 nm, A-scan rate: 50 kHz, output: 25 mW, coherence length: 12 mm)

Optical coherence tomography of a sample can be performed using the OCT device of the present disclosure. The present disclosure also relates to an optical coherence tomography method using the OCT device of the present disclosure described above.

In the optical coherence tomography method of the present disclosure, even when a user performs tomography while carrying the part (for example, a probe) having the objective lens, a difference in the environment between the sample optical path and the reference optical path does not occur, resulting in a tomography obtained. Image shift is small. Also, tomography can be performed over a wide area at one time.

The OCT device and optical coherence tomography method of the present disclosure can be suitably used in general optical coherence tomography regardless of field. As described above, even when a part of the OCT device is portable, it is difficult to generate misalignment of tomographic images and can take tomography over a wide area at once, so that it can be used particularly suitably in the industrial field.

Example

Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited only to these examples.

Example 1

Using an OCT apparatus having the configuration shown in FIG. 2, a polytetrafluoroethylene (PTFE) layer with a thickness of 3.1 mm, a tetrafluoroethylene/hexafluoropropylene copolymer (FEP) layer with a thickness of 0.4 mm, and a thickness of 4.3 mm OCT imaging was performed from the PFA layer side of a fluororesin sheet having a thickness of 7.8 mm, a length of 25 mm and a width of 25 mm, in which tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer (PFA) layers of were laminated in this order. The obtained tomographic image (length 8 mm x width 8 mm) is shown in FIG. 4 .

The details of the OCT device used and imaging conditions are shown below.

Sweep laser light source for OCT: center wavelength: 1310 nm, sweep width: 100 nm, A-scan rate: 50 kHz, output: 25 mW, coherence length: 12 mm

Objective lens: Fθ lens (trade name: LSM04 manufactured by Thorlabs), effective wavelength range (1250 to 1380 nm), effective focal length (54 mm)

Reference member: made of quartz glass, cylindrical cylinder shape, diameter 20 mmφ, length 20 mm

Optical fiber: made of quartz glass, 10 m long

Filming temperature: 26℃

Distance between reference plane and sample: 0 cm

Other shooting conditions: luminance 100, contrast 30

Comparative Example 1

OCT imaging was performed in the same manner as in Example 1 except that the objective lens was changed to an achromatic lens (trade name: AC254-050-C manufactured by Thorlabs, effective wavelength range: 1050 to 1700 nm, effective focal length: 50 mm) instead of an Fθ lens. did The obtained tomographic image (length 8 mm x width 8 mm) is shown in FIG. 5 .

In FIG. 4, the entire tomographic image is clear and uniform, whereas in FIG. 5, there is a lot of noise except for the portion surrounded by the broken line, and the effective field of view is narrow (wide-area tomography is not performed).

Comparative Example 2

OCT imaging was performed in the cross-sectional direction of a fluororesin tube having an outer diameter of 12 mm and an inner diameter of 8 mm by using an OCT device having the configuration shown in FIG. 1 and heating only the optical fiber of the sample arm at 40° C. with a dryer. The resulting tomographic image is shown in FIG. 6 .

The details of the OCT device used and imaging conditions are shown below.

Sweep laser light source for OCT: center wavelength: 1310 nm, sweep width: 100 nm, A-scan rate: 50 kHz, output: 25 mW, coherence length: 12 mm

Objective lens: Fθ lens (trade name: LSM03 manufactured by Thorlabs), effective wavelength range (1250 to 1380 nm), effective focal length (36 mm)

Optical fiber (sample arm, reference arm): made of quartz glass, length 4 m

Filming temperature: 26℃

Other shooting conditions: luminance 100, contrast 30

Reference example 1

OCT imaging was performed in the same manner as in Comparative Example 2 except that the optical fiber of the sample arm was not heated. The resulting tomographic image is shown in FIG. 7 .

In FIG. 6 where a temperature difference between the arms was generated, compared to FIG. 7, the tomographic image of the tube drifted upward in the depth direction by 2 mm or more, and the portion corresponding to the surface layer portion of the tube protruded out of the screen. In addition, in FIG. 6, an artifact (an image of an inverse arc at the top of the image), which is reflection noise, is also visible.

10: OCT device
11: light source
12, 17: coupler
13, 15: circulator
14: reference mirror
16: sample
18: photodetector
100: OCT device
101 frequency scanning light source
102: coupler
103: circulator
104: probe
105: collimator
106: galvano mirror
107: objective lens
108: reference member
109: reference plane
110: sample
111: galvano mirror driver
112: variable optical attenuator
113: differential light detection amplifier
114 PC
115: mobile display
201: user
202: probe
203 optical fiber
204: wires
205: galvano mirror driver
206: housing

Claims (11)

An objective lens for condensing light from a light source onto a sample is provided;
An optical coherence tomography device that performs tomography of the sample based on interference between sample light, which is reflected light from the sample, and reference light, which is reflected light from a reference surface provided between the objective lens and the sample,
Both the sample light and the reference light pass through the objective lens,
The objective lens is an optical coherence tomography apparatus that is an Fθ lens. According to claim 1,
The optical coherence tomography apparatus configured to perform the tomography with a distance between the reference surface and the sample set to 0 to 3 cm. According to claim 1 or 2,
The optical coherence _{tomography apparatus} of According to any one of claims 1 to 3,
The optical coherence tomography apparatus in which both the sample light and the reference light are generated from light from the light source passing through the objective lens. According to any one of claims 1 to 4,
The interference is an optical coherence tomography apparatus that is constructive interference. According to any one of claims 1 to 5,
Further, a circulator is provided that outputs light from the light source to the side of the objective lens and outputs the sample light and reference light that have passed through the objective lens to the side of a detector that detects the sample light and reference light. optical coherence tomography device. According to any one of claims 1 to 6,
Further, a coupler is provided to split the light from the light source into split light 1 used to generate the sample light and reference light, and split light 2 used to remove the DC component of the interference signal, wherein the split light 1 and the split light 2 are split. An optical coherence tomography apparatus having an intensity ratio of light 2 of 90:10 to 99:1. According to any one of claims 1 to 7,
An optical coherence tomography apparatus configured to allow a user to perform the tomography while carrying a portion including the objective lens. According to claim 8,
A part having the objective lens to be carried and a part not to be carried are connected via an optical fiber;
An optical coherence tomography apparatus in which light from the light source and the sample light and reference light are transmitted through the optical fiber. According to claim 9,
When the length of the optical fiber is 3 m or more, and the temperature difference between the atmosphere around the part equipped with the objective lens carried and the atmosphere around the part not carried is 1 ° C. or more, the deviation of the optical coherence tomography image obtained is An optical coherence tomography device of 100 μm or less. An optical coherence tomography method using the optical coherence tomography apparatus according to any one of claims 1 to 10.

Images